In recent years, cellular phones and portable information terminals equipped with the imaging device using the solid-state image sensing element, such as CCD type image sensor or CMOS type image sensor are spreading. Further these days, miniaturization of the solid-state image sensing element used for these imaging devices progresses, and for the sensor of VGA format of which effective image pixels are 640×480, the solid-state image sensing element of 1/10 inch size (pixel pitch of 2.2 micrometers) or 1/12 inch size (pixel pitch of 1.75 micrometers) is produced commercially. In connection with this, the demand to further miniaturization and the reduction in cost is increasing also to the imaging lens with which such imaging devices equip.
As the imaging lenses for such the use, single lens structured imaging lenses which can be miniaturized and are advantageous from a viewpoint of the reduction in cost are proposed rather than 2 lens structured imaging lenses. Further in recent years, like the wafer technology of an image pick-up sensor, methods for further reducing the cost by forming a plurality of such the small imaging lenses in bloc and individualizing them by cutting is proposed.
Thus, for attaining the cost reduction of the imaging lenses formed in block and individualized as mentioned above, it is effective to simultaneously mount the imaging lenses with other electronic components, such as IC chip on a substrate by using a reflow processing the substrate performed potting these components in advance. Therefore, it is attracted attentions that plural imaging lens formation using the joint type compound lens on which energy curable resin, such as light curable resin and heat curable resin, is pasted up on the surface of the glass substrate is adapted to the reduction in cost, and the reflow processing.
These joint type compound lens have a large merit in the points that they can be produced with a lower cost compared with glass mold lenses, that, with respect to the strength, they are superior to lenses integrally formed of resin, and that the further improvement of the optical characteristics and the further miniaturization can be attained because the optical characteristics can be adjusted with flexibility not only by the shapes of the lenses but also by the selection of the joining material. Some are known as a prior art of the imaging lens which consists of such a single joint type compound lens (for example, refer to the patent documents 1 and 2).